DE2503244A1 - PHOTOGRAPHIC CAMERA - Google Patents

Description

PATENT LAWYERS

O E Π OO A A Dr.-lng. Wolff

.. 3 ν, / g c * tt _{H beard} | _s

Dipl.-Chem. Dr. Brandes Dr.-lng. hero Dipl.-Phys. Wolff

D - 7 Stuttgart 1, Lange Strasse 51

Tel. (07 11) 29 6310 and 29 72 95

Telex 07 22312 (patwod)

Telegram writer

tlx 07 22312 Wolff Stuttgart

PA Dr. Brandes: Headquarters Munich postal check account Stgt. 7211-700 Deutsche Bank AG, Stuttgart. 14/28630

Office hours:

9-11.30 a.m., 1.30 p.m.-4 p.m.

except saturdays

January 23, 1975 Our ref .: 124 563/487333 kdk

Eastman Kodak Company, Rochester, New York State,
United States of America

Photographic camera

Telephone information and

509831/0662 orders are only available after written

Confirmation binding

The invention relates to a photographic camera whose Shutter by means of a light-sensitive shutter control circuit having a photoconductive component, whose photosensitivity is changeable, controllable in such a way that one is in inverse proportion to Strength of the scene light brightness standing exposure time is obtained.

For cameras that are intended for hand-held photography and that have automatic exposure control devices have, the endeavor in technology is to train such cameras so that the camera user an indicator signal is made available which indicates whether the scene brightness is sufficient for an exposure within a predetermined time interval, i.e. within a predetermined range of exposure times, to be able to do or not. Having such an ad available makes sense because of the quality of the photographic image in the case of a hand-held picture depends in part on the extent to which the Operator of the camera is able to keep it steady during the exposure time. High quality recordings can usually only be obtained with certainty from the hand if this predetermined time interval is 1/30 second does not exceed. The operator of the camera is often unable to use the camera for a long period of time To keep a period of 1/30 of a second at rest, so that when taking pictures with exposure times that exceed 1/30 of a second, the image of the subject recorded on the film is blurred or blurred, resulting in a corresponding loss in resolving power.

There are already cameras with shutter control circuits known see, for example, U.S. Patents 3,245,332 and 3,500,729, in which, in view of this fact, the time interval

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all of which are available for the camera in question Exposure times includes, is limited to a fixed value, so that by the shutter control circuits of these cameras the film exposure is ended at the latest after a predetermined time interval of, for example, 1/30 second. These known cameras have except the light-sensitive Shutter control circuit has a second shutter control circuit, which operates insensitive to light, and a fixed one Has a time constant of 1/30 of a second. If the shutter is opened while these cameras are in operation, both of them become these Lock control circuits put into operation. Each of the two shutter control circuits begins after it has been activated, a control signal to close the Generate closure. Depending on which of the two shutter control circuits this signal with a predetermined signal amplitude is the first to be available, it closes of the shutter from either the photosensitive shutter control circuit or the non-photosensitive one Shutter control circuit. The latter is the case after 1/30 of a second when the scene brightness is so low that the photosensitive shutter control circuit not within this time interval of 1/30 second in turn the relevant Generated signal.

With such cameras it is achieved that the shutter is closed in any case after a time interval of 1/30 of a second. It goes without saying that very strong Underexposed recordings can be obtained when the scene brightness is very low.

In a known camera of the type mentioned in the opening paragraph, which is shown in US Pat. No. 3,326,103 for the purpose of reducing the exposure time with low scene brightness, as it prevails, for example, when the camera has a flash

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is used, the arrangement is made so that one associated with the camera depending on the start-up Flashlight device .the light-sensitive shutter control circuit the camera is affected. In this known camera, the shutter control circuit is influenced in such a way that their photosensitivity is partially retained, that is, the photosensitivity of the shutter control circuit is changed. This change in light sensitivity takes place in this known camera of the type mentioned in that, depending on the attachment of the associated flash device to the camera an electrical, light-independent resistor is placed in parallel with the photoresistor of the shutter control circuit. This is for the RC time constant of the time generator the shutter control circuit has a total resistance effective, the resistance of which is both less than that Resistance of the light-independent resistor as well as that of the photoresistor. Are now flash photos taken with such great scene brightness, where the natural Scene light is sufficient to complete the exposure process within a predetermined time interval, then Most of the current that charges the timing capacitor of the shutter control circuit flows through the light-dependent photoresistor j and that through the fixed or Light-independent resistance flowing current plays a smaller role in relation to influencing the exposure time. However, if the natural scene brightness is insufficient to obtain a correct exposure within the predetermined To bring the time interval to completion, then the resistance of the light-dependent photoresistor is proportionate high, so that the fixed or light independent resistance in controlling the exposure time under these operating conditions low natural scene brightness plays a greater role. As a result, the presence of the light

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independent resistance limits the maximum exposure time to a certain value.

The fact that the exposure time is limited to a maximum value by the fixed resistance even in the case of extremely low scene brightness, that is to say even if there is practically no natural scene brightness, is an advantage. However, since the fixed or independent resistance permanently influences the shutter control circuit in the same way, even if the scene brightness is greater, underexposed images are obtained in the operating states of the camera in which the natural scene brightness is sufficient for a correct exposure within of the predetermined ^{time interval of 1} / 30th of a second to complete.

The photosensitivity of a photographic film concerned can be determined by the relationship between the density, i.e. the Opacity of the developed film, and the logarithm of the exposure be expressed. When this relationship is graphed, it usually results in a curve in shape of an inclined, elongated S. Such a D over log. E curve represents the sensitivity characteristics of the film in question. Then, as is known, the film in question is properly exposed when the exposure in the rectilinear Part of this curve. This area of the curve has the highest image contrast and therefore generally the greatest Resolving power of the film reached.

Many of the films commercially available today have one large exposure width, which makes it possible in cases of underexposure or overexposure to a limited extent, these exposure errors by special film

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to compensate for winding / that a perfectly developed film is obtained. This can be achieved by one selectively some of the parameters of the film development process changes in a known manner. But even when these compensation methods are used, the known ones are used Cameras of the type described in U.S. Patents 3,245,332 and 3,500,729, i.e. with a fixed limitation of the maximum exposure time to 1/30 of a second, not in many cases possible to get usable images because the differences between the correct exposure times are too great and the actual exposure time. When using the known camera of the type mentioned above, As shown in US Pat. No. 3,326,103, the ratios are more favorable because for all sizes of the scene brightness, the difference between the correct exposure time and the actual exposure time is limited and thus the compensation methods mentioned above can often still be used with success are. A serious disadvantage here, however, is that even with such values for the scene brightness, the allow the exposure to be completed within the 1/30 second time interval, an exposure error occurs due to the presence of the fixed, light independent resistor.

The invention is based on the object of creating a camera of the type in question in which not only is it ensured is that the shutter moves from the open to the closed state even at the lowest values of the scene brightness is transferred, but with which it is also ensured that over a larger range of low scene brightnesses Recordings can be made using the compensation methods customary in film development, at least if necessary can be used to produce good photographic images.

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In the case of a camera of the type mentioned at the outset, this is the task resolved according to the invention in that the shutter control circuit has a trigger circuit which on is responsive to the presence of a predetermined level of brightness of the scene lighting and in dependence thereon Respond the photosensitivity of the shutter control circuit is changed if and only if the The intensity of the scene brightness falls below the predetermined brightness level. The fact that this automatically the Photosensitivity of the shutter control circuit is only influenced if this is due to the prevailing in question Scene brightness makes sense, becomes the usable work area or application area the camera is extended in the area of low visualities, without having to accept an incorrect exposure in the areas of higher scene brightness, as this is the case with the known camera of the type mentioned at the beginning.

The selective one, depending on the response of the trigger circuit Any change in the photosensitivity of the shutter control circuit can be made by an electrical auxiliary signal generated by the response of the trigger circuit be made.

To generate the electrical auxiliary signal, an electrical * - shear resistance can be provided for changing the Photosensitivity of the shutter control circuit can be switched in parallel to the photoconductive component thereof.

The camera according to the invention also makes it possible in an advantageous manner Way, the generation of a display signal that the operator knows whether the strength of the scene brightness is large enough to flawlessly take pictures from the

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To be able to do it by hand or not. For this purpose, the arrangement of the camera according to the invention can be made in this way be that a light source that can be actuated as a function of the response of the trigger circuit for generating the display signal is provided.

According to a further preferred embodiment, can The light source also serves to selectively change the photosensitivity of the shutter control circuit to get in the way you want. This is achieved by changing the photosensitivity of the Shutter control circuit whose photoconductive component can be illuminated by the light source. It becomes in a particularly simple structure of the camera according to the invention is advantageously achieved.

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The invention is explained in detail below with reference to the drawing explained.

Show it:

Fig. 1 is a diagram in which the exposure time photographic footage as Function of the scene brightness is applied.

FIGS. 2 and 3 are schematic block diagrams the electrical circuit of two embodiments of the invention Camera and

FIG. 4 shows a diagram representation similar to FIG. 1.

Since photographic cameras come in many forms are 'known, the present description is mainly aimed only at those camera parts that are directly belong to the invention or are more closely related to it. It is understood that not specifically shown or described camera parts in the usual, the Can be designed in a manner known to those skilled in the art.

A curve drawn in FIG. 1 as a solid line shows the correct or ideal exposure time of a photographic Film material as a function of scene brightness. A curve denoted by 12 and drawn in dashed lines shows the exposure time as used using those disclosed in U.S. Patents 3,245,332 and 3,500,729 Cameras is obtained. One shown in phantom in Fig. 1 Curve 14 shows the exposure time using that known from US Pat. No. 3,326,103 Camera is obtained.

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Fig. 2 shows a circuit designated as a whole with 20, which _{is supplied with electrical energy by means of a battery 21 after actuation of a normally open switch S 1} and which is used to automatically control an electronic shutter mechanism 22 of the associated camera. The locking mechanism 22 may be of any known type, for example of the type known from referenced U.S. Patents 3,245,332 and 3,326,103, or of the type shown in U.S. Patent 3,748,974 is known. Such shutter mechanisms essentially have a pair of opaque shutter blades, one of which is referred to as an opening blade and one as a closing blade, and which are arranged to be movable relative to an objective opening in order to selectively the amount of the object through the recording! ν of the scene light falling through the camera, which is thrown against the film plane of the camera. The opening lamella can preferably be actuated mechanically by a shutter release member in order to initiate an exposure interval during which time the film is exposed. The shutter blade can be electromechanically actuable, for example by sequentially energizing and de-energizing an electromagnet in order to terminate the exposure interval when a predetermined amount of scene light has impinged on the film. Such locking mechanisms are only briefly mentioned here with regard to their mode of operation in order to make the present invention and the intended type of application of the same even better understood.

With the shutter mechanism 22 is a shutter control circuit 24 effectively coupled, which works depending on the light, around the closing lamella according to the amount of light in the scene which is thrown against the film plane of the camera. As shown, the shutter control

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circuit 24 has a photoconductive component 26 which is connected between a terminal 28 and a terminal 30 of the circuit 20. With the connection .30 is also a Input 32 of a voltage-sensitive trigger circuit 34 connected. Between the connection 30 and a ground connection 36 there is a capacitor serving as a time generator and a normally closed switch S_ is switched, which can be switched to the open switch position when the opening blade of the shutter is moved to the open position in order to initiate the exposure interval.

It goes without saying that the normally open switch S and the normally closed switch S ₂ are arranged so that they can be actuated one after the other by manually releasing a shutter release member (not shown) or some other known release device. If the switch S is closed at the beginning, the switch S_ remains closed for a short period of time for a reason to be shown below.

The photoconductive member 26 can be a any such component of a known type, as used for light measuring Devices in photographic equipment are in use, act, for example, to a photoresistor or the like with an electrical resistance that is inversely related to the level of the incident light. That photoconductive component 26 and the capacitor 38 serving as a time generator form an RC integrating circuit which due to the aforementioned photoconductive properties, has a time constant that is inversely related the strength of the scene light and is used to generate an electrical control signal at the terminal 30, the has an amplitude related to the intensity of the scene light and time.

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The trigger circuit 34 may be a known one Act comparison or comparator circuit, for example a Schmitt trigger or the like, with one normally non-conductive input stage and one normally conductive output stage are provided to keep the closing blade of the shutter in its open position. As long as the signal at terminal 30 is below a predetermined signal level, i.e. below a threshold voltage, the input stage is in the "Off" state, whereas the output stage is in the "On" state. When the signal exceeds the threshold voltage, the output stage is switched to the "Off" state, causing the shutter released xmd the camera shutter is closed.

With the shutter control circuit 24 is a light level display circuit 42 operatively coupled, which serves to indicate that the scene light is sufficient to to enable perfect film exposures by hand within a predetermined exposure interval, for example 1/30 second or less. In addition, the display circuit 42 serves to show the time dependency for the control signal of the shutter to modify if the strength of the prevailing scene light is too low to to allow such a film exposure (that is, an exposure time not exceeding the predetermined time interval).

The display circuit 42 has a pnp transistor A4 with an emitter 44a, a base 44b and a collector 44c. The emitter 44a is connected to the terminal 28. The base 44b. is connected to a terminal 46 and the collector 44c is connected to a current limiting one

Resistor 47 connected, in turn in the manner shown ... . with the

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Capacitor 38 is in communication. A light source 48 is connected between the terminals 28 and 46, for example a light source in the form of an indicator lamp _/ a light emitting diode (LED) or the like, in order to obtain an indication that the intensity of the scene light is sufficient to obtain a correct film exposure within the above mentioned, predetermined time interval of 1/30 second to enable. An output 49 of a trigger circuit 50 is also connected to the terminal 46, which is similar to the aforementioned Schmitt trigger, but differs therefrom in that the trigger circuit 50 has an inverse functional relationship between its input stage and its output stage, ie is the trigger circuit 50 of such a kind that its input stage is normally conductive, so that the trigger circuit (in its output stage) only conducts when the input signal fed to the trigger circuit is greater than a certain preselected threshold voltage, which may have a different value than the threshold voltage the trigger circuit 34 is the case. As shown, the trigger circuit 50 has its input 51 connected to a terminal 52 to which a resistor 53 serving for voltage control and a photoconductive component 54 are also connected in the manner shown. When switch S is closed, the series circuit of photoconductive element 54 and resistor 53 acts as a voltage divider to produce an instantaneous voltage at terminal 52 of a relatively fixed value which is inversely related to the resistance of photoconductive element 54 This voltage is directly related to the intensity of the scene light illuminating photoconductive member 54.

In order to explain the function of the display circuit 42, it is necessary to determine two levels of the intensity of the scene lighting to consider. The electrical properties of the

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Resistor 53 and the photoconductive member 54 are selectively influenced so that the instantaneous voltage only then holds the normally conductive input stage of the trigger circuit 5O in the "on" state at connection 52, when the intensity of the scene light is sufficient to obtain a correct exposure within the specified time interval of 1/30 of a second. If the intensity of the scene light is not sufficient for this, the current is in the photoconductive member 54 is relatively small, thereby causing a relatively small signal voltage occurs. When it does, the normally non-conductive output stage becomes the trigger circuit 50 switched to the "on" state, creating an electrical circuit through the light source 48 and through the Trigger circuit 50 through to ground terminal 36 is closed to turn on the light source 48. When this is the case, the voltage on terminal 46 drops by the amount of voltage drop that results across the light source 48, thereby causing the transistor 44 is switched on or conductive and a collector current flows through resistor 47 to terminal 30.

From the above description of the operation of the display circuit 42 it can be seen that the transistor ^ A is not conductive when the intensity of the scene light is sufficient to allow proper exposure within the 1/30 second time interval.

The operation of the shutter control circuit 24 will now be considered in the event that the light source 48 is in Activity is located to indicate the strength of the scene light is low (i.e. too low to obtain a correct exposure within the time interval of 1/30 second

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possible). As soon as the switch S _{2 is} actuated, that is to say opened, the capacitor 38 begins to charge immediately, the rate at which the charging takes place in an inverse proportion to the product of the

Capacitance and resistance of the photoconductive member 26, that is, charging occurs at a rate related to the intensity of the scene light stands. When the intensity of the scene light * is not sufficient to obtain a correct exposure within the time interval of 1/30 of a second then this product is large and capacitor 38 charges very slowly on. However, since the collector current flowing through the resistor 47 with the current of the photoconductive member 26 at Terminal 30 is combined, the capacitor 38 is accelerated to the threshold voltage of the trigger circuit 34 charged.

It can be seen that in an environment where the scene light is insufficient to obtain a correct exposure within a time interval of 1/30 second, the light source 48 performs the function of the camera operator of the presence of this operating condition or this To bring the ambient condition to the knowledge _# -and that the light source here also serves to generate an auxiliary signal or an auxiliary current in order to obtain a shortening of the exposure interval, the exposure duration being functionally related to the prevailing scene lighting conditions.

As mentioned above, it is possible to a certain extent develop underexposed films so that a good, usable photographic image is obtained. The object described here now makes it possible to produce a photographic image of high quality with selective influencing

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Solution of parameters in film development over a wide range of low scene light intensities without this would impair the formation of the correct exposure times in scene lighting conditions that are sufficient to to allow correct exposure in less than a 1/30 second time interval. This result can perhaps best be clarified with reference to FIG. 4 and the curves shown therein, which refer to FIG a qualitative basis should enable a comparison between the size of the area of low scene brightness, over that a good photographic image can be achieved with a control circuit of the type described here, see curve 16

,, -, / the size of the. area in which di, es can be and / with an exposure control device of the type of the aforementioned US Pat. No. 3,245,332, see curve 12, can be reached. It will of course be understood that if the scene lighting conditions are suitable, a correct Exposure within a time interval of less than 1/30 of a second to allow the actual exposure time corresponds to the ideal or correct exposure time and therefore there is no need to change the development parameters to be modified in such scene lighting conditions, as is the case, for example, with the one described in US Pat. No. 3,326,103 The exposure control device shown is necessary, the mode of operation of which is illustrated by curve 14 in FIG. 1.

Another preferred embodiment shown in FIG. 3 is now contemplated. In this 1 and 2 are components that are similar in structure or function to corresponding components of FIG. 2 with the same Reference numerals denoted. As shown in Fig. 3, a light guide 60 forms, for example, a light guide tube or an optical device of mirrors or the like, a device for directing light from the light source 48 onto the photoconductive member 26 to be transferred. If this takes place, then a lowering of the resistance of the photo-

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conductive component 26 due to the combined effect of the scene light and the light from the light source 48 to provide a shorter RC time constant for the shutter control circuit 24 to get. In this way, the exposure time in low scene lighting conditions is also limited. The resulting modification, however, is such that a wider range of low scene brightnesses than is the case in the embodiment shown in Fig. 2 is used for the production of good photographic images Pictures is available.

It should be noted that in the exposure control circuits shown here a certain reduction in quality can possibly occur because the exposure time is at low Scene brightness can extend over the time interval of 1/30 seconds, whereby a by the operator blurring or blurring of the recording can occur on the film. However, it was found that the loss of resolution in the photographic image is more than offset by the fact that over a A more suitable exposure .of the film is made available, so that overall Higher quality photographic images can be achieved by the circuits shown here.

This is perhaps best understood by the fact that those filra exposures where the greatest expansion of the exposure time over the interval of 1/30 of a second and with which there is therefore the greatest risk of blurring or blurring, too those exposures or shots are the strongest would be underexposed if one were to work with a fixed "longest exposure time and which would result in the most unsightly pictures. Those pictures,

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in which the smallest extension of the exposure time takes place beyond the time interval of 1/30 seconds not only show those recordings that are easiest to correct with known development techniques, but also have the least amount of camera shake.

In Fig. 4, with (A) is the size of the range of the scene brightnesses indicated, in which after falling below the predetermined brightness level (the predetermined time interval of, for example, 1/30 of a second) usable photographs can still be taken, when a known camera of the type described in U.S. Patent Nos. 3,245,332 or 3,500,729 is used. With (B) is the enlarged area that can be used when using the camera shown here. (C) shows the increase that results here for the size of the usable area.

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Claims (7)

Claims (lj Photographic camera, the closure of which by means of a photosensitive shutter control circuit comprising a photoconductive component, its photosensitivity is changeable, is controllable in the way, that an exposure time in inverse proportion to the intensity of the scene brightness is obtained, thereby characterized in that the shutter control circuit (24) has a trigger circuit (50) which responds to the presence a predetermined brightness level of the scene lighting responds and, depending on their response, the light sensitivity of the shutter control circuit (24) then and only is changed when the strength of the scene brightness falls below the predetermined brightness level. 2. Camera according to claim 1, characterized in that to change the light sensitivity of the shutter control circuit (24) an electrical auxiliary signal generated by the response of the trigger circuit (50) is provided. 3. A camera according to claim 2, characterized in that an electrical auxiliary signal is used to generate the electrical auxiliary signal Resistance (47) is provided, which is used to change the light sensitivity of the shutter control circuit (24) parallel to their photoconductive component (26). is switchable. . 4. Camera according to claim 3, characterized by a transistor (44) controllable by the trigger circuit (50), whose collector-emitter branch is connected in parallel with the photoconductive component (26) and with its collector (44c) the electrical resistor (47) is connected in series. S09831 / 0662 5. Camera according to one of claims 1 to 4, characterized in that that a depending on the response of the trigger circuit (50) actuatable light source (48) for Generation of a visible, falling below the predetermined Brightness level indicating display signal is provided. 6. Camera according to claim 5, characterized in that for changing the light sensitivity of the shutter control circuit (24) whose photoconductive component (26) can be illuminated by the light source (48). 7. Camera according to claim 6, characterized in that a Light from the light source (48) on the photoconductive component (26) transmitting light guide (60) is provided. 509831/0662 Blank page